The U.S. Pat. No. 5,284,429, to Schneider et al., discloses a mold and gas pin assembly for use in the injection molding of a thermoplastic article. A fluid supply passageway is provided in the mold to allow fluid to be ejected through and communicated to either the thermoplastic flow path or into the article-defining cavity. An end passage of the thermoplastic flow path has a plug disposed therein. The plug includes a porous core which permits the flow of low viscosity fluid such as a gas therethrough, but prevents the passage of molten thermoplastic therethrough. In one embodiment, the plug is threaded into the passageway end portion. When the porous core of the plug becomes substantially filled with thermoplastic, the plug is easily removed and replaced in the first embodiment by merely unthreading the plug. In a second embodiment, the plug is replaced by unthreading two or four fasteners which secure the plug to the stationary mold half. However, in each of these embodiments, in order to service the core, the entire plug must be replaced. In a third embodiment, the core may be serviced but the entire mold half in which the core is secured must be disassembled.